Clumping animal litter and method thereof

ABSTRACT

A clumpable animal litter comprises composite particles of filler materials, such as limestone and sand, and sodium bentonite. The filler materials have a lower bulk density as compared to a granular mixture of the same percentage of filler and sodium bentonite clay and contain up to eighty-five percent less clay.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/409,308, filed Jan. 18, 2017, which claims the benefit of U.S.Provisional Application No. 62/286,200, filed Jan. 22, 2016, each ofwhich is hereby incorporated by reference in its entirety.

THE FIELD OF THE INVENTION

Disclosed herein are clumpable animal litters. Specifically, disclosedherein are animal litters comprising composite particles of fillermaterials, such as limestone and sand, and sodium bentonite that performas well as traditional clay-based, clumping litters, yet have a lowerbulk density as compared to a granular mixture of the same percentage offiller and sodium bentonite clay and contain up to eighty-five percentless clay.

RELATED ART

Clay has long been used as a liquid absorbent and has found particularusefulness as an animal litter. Typically, the clay is mined, dried, andcrushed to the desired particle size. Some clay litters have the abilityto clump upon wetting. For example, sodium bentonite is awater-swellable clay which, upon contact with moist animal waste, isable to agglomerate with other moistened sodium bentonite clayparticles. The moist animal waste is contained by the agglomeration ofthe moist clay particles into an isolatable clump, which can be removedfrom the container (e.g., litter box) housing the litter. The clumpstrength of clay litters containing equal or greater than ninety percentsodium bentonite are strong enough to hold the clump shape upon contactwith moisture and retain that shape upon scooping without pieces of thelitter breaking off of the clump and remaining in the litter box,allowing waste therein to create malodors. However, sodium bentoniteclay is very heavy and is mined. As such, it is a limited resource.

Another problem inherent in typical sodium bentonite clay litters is theinability to effectively control malodors. Clay has very poorodor-controlling qualities, and inevitably waste build-up leads tosevere malodor production. What is needed is an animal litter that usesless sodium bentonite with effective odor-controlling properties.

Accordingly, what is needed is an absorbent material suitable for use asan animal litter that uses less sodium bentonite, yet has clumpingcharacteristics equivalent to clay-based litters that contain at leastninety percent sodium bentonite. What is further needed is an animallitter with odor-controlling properties that has clumping propertiescomparable to clay-based litters containing greater than ninety percentsodium bentonite, yet that requires much lower concentrations of sodiumbentonite. What is further needed is an animal litter containingcomposite particles of sodium bentonite and filler material (e.g.,limestone) that has lower bulk density relative to an animal littercontaining the same percentage of a dry blend of sodium bentonite andfiller material.

U.S. Pat. No. 4,671,208 discloses an absorbent cat litter that containsclay and limestone. US2006042553 discloses a cat litter that containsground limestone and a thickener that is digestible by cats. Neitherdiscloses an animal litter with the odor-controlling, bulk densities andclumping properties disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the non-linear relationship between limestone content andbulk density of the composite particles.

FIG. 2 shows a comparison of product bulk density when dry added andwhen agglomerated.

FIG. 3 shows the non-linear relationship between particle attrition andlimestone content tested using a modification to ASTM method E-728Standard Test Method for Resistance to Attrition of Granular Carriersand Granular Pesticides as described below.

FIG. 4 is a graph showing the clump strength of animal litter as afunction of limestone content.

FIG. 5 shows SEM pictures demonstrating the elemental map of theparticles as a function of limestone content.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing embodiments of the present invention in detail, it isto be understood that all publications, patents and patent applicationscited herein, whether supra or infra, are hereby incorporated byreference in their entirety to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated by reference in its entirety.

It must be noted that, as used in this specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the content clearly dictates otherwise. Thus, for example,reference to an “additive” includes two or more such additives.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention pertains. Unless otherwise stated,amounts listed in percentage (“%'s”) are in weight percent.

Disclosed herein are composite absorbent particles that comprise asodium bentonite component and a “filler material” (as defined herein)component. Optionally, additives, such as, powdered activated carbon“PAC” (as defined herein), can also be added to the composite absorbentparticles.

The composite absorbent particles have improved physical and chemicalproperties such that a litter can be produced without compromising theperformance of traditional clumping clay-based litters that containequal or greater than ninety percent sodium bentonite. Although sodiumbentonite-based litters clump well, they also have disadvantages. Sodiumbentonite is relatively expensive, limited in terms of geographicavailability, and not a renewable resource.

Disclosed herein are composite absorbent particles comprising betweenabout thirty and about seventy percent by weight sodium bentonite thatmaintain the clumping benefit of “pure sodium bentonite” (as definedherein). In one an embodiment, a composite particle animal litter isdisclosed that comprises as little as twenty percent by weight sodiumbentonite, yet retains the majority of the clump strength of pure sodiumbentonite litter. In preferred embodiments, a composite particle animallitter is disclosed that comprises as little as thirty percent by weightsodium bentonite, yet retains the clump strength of pure sodiumbentonite litter. A high shear agglomeration process may be used to makethe composite particles disclosed herein, such as pin mixing.

As used herein the term “pure sodium bentonite litter” means a clumpingclay-based litter that contains equal or greater than ninety percent byweight sodium bentonite. As used herein, the term “granular sodiumbentonite” means sodium bentonite clay that is either (a) mined, crushedand sieved or (b) processed by methods know in the industry to asuitable particle size (about 3 mm to about 0.4 mm) to be used asclumping animal litter. As used herein the term “composite particle”means a discrete particle that is formed by the combination of smallercomponent particles.

As used herein the term “PAC” means powdered activated carbon that is afine black powder made from wood or other carbon-containing materials(e.g., coconut, coal, etc.) that have been exposed to very hightemperatures in an airless environment and treated, or activated, toincrease its ability to absorb by reheating with oxidizing gas or otherchemicals. The result is a highly porous fine powder with a particlesize less than about 0.25 mm and typically ranging from about 50 toabout 150 microns.

As used herein the term “clump strength” means the percentage ofparticles retained in the clump after three hours using the clumpstrength test method described herein.

As used herein the term “high shear agglomeration process” means a highspeed, conditioning and micro-pelletizing device that converts powderinto small agglomerates through the action of a high speed and theaddition of water. As used herein the term “component” when used inconjunction with a composite particle means a small particle of onematerial that was combined with other small particles of itself and/orof small particles of different materials to form a composite particle.As used herein the term “spacer material” means an agent that helpsspread sodium bentonite on the surface of a filler material componentfor better distribution of the sodium bentonite during the agglomerationprocess.

As used herein the term “binder” means a substance that causes thecomposite particles to better adhere to each other upon contact with aliquid, such as water or urine, to form a strong chimp. Examples ofbinders include guar gum, starch, modified starch, naturalhydrocolloids, alginates, acrylates, and polyvinyl acetate. Particlesize ranges are determined by screening methods known in the art.

Filler Materials

As used herein, the term “filler material” means a non-absorbentmaterial that is more readily available than bentonite and used toreplace a portion of a more expensive or scarce component of a catlitter formulation. Examples of suitable filler materials includelimestone, dolomite, calcite, calcium carbonates, sand, shale, gravel,slate.

High shear agglomeration processes includes pin mixers, pelletizers,extruders, etc. . . . such an agglomeration process can be used to formdiscrete composite particles. Pin mixing is a pin-type, high speed,conditioning and micro-pelletizing device that converts small particles(“components”) into discrete agglomerates (“composite particles”)through the action of high speed and the addition of water.

Sodium Bentonite

Sodium bentonite powder having a mean particle size less than about 0.25mm is preferred. Sodium bentonite expands when wet, absorbing as much asseveral times its dry mass in water. The main mineral that formsbentonite is Montmorillonite ((Na,Ca)_(0.33)(Al,Mg)₂(Si₄O₁₀)(OH)₂.nH₂O).Sodium Montmorillonite (Na-montmorillonite), in particular, expandsconsiderably more than other clays, e.g., Calcium Montmorillonite(CA-montmorillonite) due to water penetrating the interlayer molecularspaces and concomitant adsorption. The presence of sodium as thepredominant exchangeable cation can result in the clay swelling toseveral times its original volume. Hence, its application in animallitters.

Adding a small amount of binder, such as guar gum, in an amount aslittle as 0.1 percent by weight can increase the clump strength of theresulting litter in some cases by up to ten percent. Preferred bindersinclude guar gum, starch, polyacrylates, polysaccharides, and alginates.Guar gum (“guar”) is particularly preferred because it is a powderedsolid that helps form strong and rigid clumps when wet and tends to bevery evenly distributed throughout the resulting composite particles.Thus, a very small amount of guar can have a considerable impact.Binders, such as guar, are known for their binding properties. They havebeen used in several cat litters to facilitate the adhesion betweenparticles thus, clumping. However, none of these composite particles(e.g., filler materials, such as limestone or sand and guar, even inmuch higher concentrations) could achieve the high absorption andimmediate clumping of sodium bentonite.

On the other hand, when using a high shear agglomeration process to mixsodium bentonite with a filler material, such as limestone or sand, theresulting composite particles are strong and clump and absorb liquid aswell as pure sodium bentonite.

The composite particles are formed using a filler material componentpreferably having a mean particle size no greater than 0.5 mm(preferably ranging from about 0.074 mm to about 0.42 mm) and a sodiumbentonite component preferable having a mean particle size no greaterthan about 0.25 mm and optionally a PAC component.

The animal litter disclosed herein comprises limestone in an amountranging from about 20 percent to about 80 percent (preferably from about30 percent to about 70 percent and most preferably from about 40 percentto about 60 percent), sodium bentonite in an amount ranging from about80 percent to about 20 percent (preferably from about 70 percent toabout 30 percent and most preferably from about 60 percent to about 40percent) by weight, and optionally PAC in an amount ranging about 0.1 toabout 2 percent (preferably from about 0.3 to about 1 percent byweight). Higher amounts of PAC can be used, but generally are not costeffective. Embodiments of such animal litter can include (1) a dry blendof absorbent material suitable for use as an animal litter (e.g., sodiumbentonite clay) and filler material/sodium bentonite compositeparticles, (2) a dry blend of absorbent material suitable for use as ananimal litter (e.g., sodium bentonite clay) and filler material/sodiumbentonite/PAC composite particles, (3) a dry blend of absorbent materialsuitable for use as an animal litter (e.g., sodium bentonite clay),filler material/sodium bentonite composite particles, and sodiumbentonite/PAC composite particles, (4) filler material/sodium bentonitecomposite particles, (5) filler material/sodium bentonite/PAC compositeparticles, (6) a dry blend of filler material/sodium bentonite compositeparticles and filler material/sodium bentonite/PAC composite particles,and combinations or modifications thereof. In embodiments where theanimal litter comprises dry blends of absorbent material and compositeparticles, the amounts of the filler material component, the sodiumbentonite component and the carbon component in the pre-blend mixture toform the composite particles would be adjusted accordingly to providethe desired percentages of each in the resulting litter composition.

Embodiments of composite particles can comprise a filler materialcomponent in an amount ranging from about 20 percent to about 80 percent(preferably from about 30 percent to about 70 percent and mostpreferably from about 40 percent to about 60 percent) by weight and asodium bentonite component in an amount ranging from about 80 percent toabout 20 percent (preferably from about 70 percent to about 30 percentand most preferably from about 60 percent to about 40 percent) byweight. Relative to each other, the resulting composite particles allcontain approximately the same level of the two components (clay andfiller material) which allows for an efficient use of the sodiumbentonite so that the amount of sodium bentonite can be significantlyreduced without substantially sacrificing the clump strength and liquidabsorbtion of the litter because the contact between component particlesof the composite particle is maximized.

Additionally, PAC can be included in the composite particles. As usedherein the term “bentonite/filler material/PAC composites” is defined asa composite particle comprising a filler material component, a sodiumbentonite component, and a PAC component. As with the fillermaterial/sodium bentonite composite particles, the resulting fillermaterial/sodium bentonite/PAC composite particles all contain (relativeto each other) approximately the same level of the three components(clay, filler material and PAC) such that the odor control efficacy ofthe carbon is not sacrificed because the distribution of the PAC withinthe composite particles is maximized. It is desired that the amount ofPAC in the animal litter is an amount ranging from about 0.1 to about 2percent (preferably about 0.3 percent to about 1 percent). If the litterwill be comprised primarily of composite particles, then the appropriateamount of carbon component would be added to the composite particlepre-blend. If the litter was intended to be a dry blend of compositeparticles and absorbent material suitable for use as an animal litter(e.g., sodium bentonite), then the amount of each component in thepre-blend would be adjusted accordingly.

Optionally, a guar gum component in an amount ranging from 0 percent toabout 1 percent by weight may be included.

It was anticipated that using a high shear agglomeration process toagglomerate a mineral-based material such as a limestone or sand and asodium bentonite component would result in a composite particle having asignificantly higher attrition than pure sodium bentonite. Contrary tothis expectation, Table 1 below shows that the attrition of thesecomposite particles is comparable to that of pure sodium bentonite.

In addition, it has unexpectedly been found that the clump strength of asample litter made by pin-mixing a sodium bentonite component and alimestone component to form a litter comprising sodiumbentonite/limestone composite particles is very near to that of puresodium bentonite.

Without being bound by theory, it is believed that the filler material(e.g., limestone, sand) components have a very limited capacity toabsorb liquids as compared to clays. It is therefore believed that theliquid will be channeled past the filler components in each compositeparticle and selectively absorbed by the sodium bentonite, with the netresult of more optimal usage of the sodium bentonite absorbancy. Thisleads to a comparable clump strength and liquid absorption to a puresodium bentonite cat litter. It is expected that a similar phenomenonwill occur even if just a portion of the litter contains the compositeparticles (e.g., a litter composition comprising a dry blend of sodiumbentonite and filler material/sodium bentonite composite particles).

Bulk density is another important property of animal litter. Bulkdensity is a property of powders, granules and other “divided” solids,especially used in reference to mineral components. It is defined as themass of the many particles of the material divided by the total volumethey occupy. The total volume includes particle volume, inter-particlevoid volume and internal pore volume. Bulk density is not an intrinsicproperty of a material; it can change depending on how the material ishandled. For example, a powder poured into a cylinder will have aparticular bulk density; if the cylinder is disturbed, the powderparticles will move and usually settle closer together, resulting in ahigher bulk density. Bulk density is a measure of the weight of thelitter per unit volume (g/cc). The test method used to measure bulkdensity comprises a hopper with a pint container underneath. The hopperis filled with approximately 2000 cc of the sample. The gate situated atthe bottom of the hopper is opened to fill the pint container withmaterial until it overflows. The container is then leveled out using astraight edge tool and the weight is recorded. The same process isrepeated twice and an average of three reps is reported (g/cc or lb/cf).

Referring to FIG. 1, the bulk density of compositions comprising sodiumbentonite and from zero to about 95% limestone were measured. FIG. 1shows the unexpected non-linear relationship between limestone contentand bulk density when limestone and sodium bentonite are agglomerated.

The bulk density of a dry added combination of limestone and sodiumbentonite was compared to the bulk density of an agglomeratedcombination of limestone and sodium bentonite. FIG. 2, shows thecomparison between the bulk densities of a dry blend and an agglomeratedblend.

Particle attrition was also measured. FIG. 3 shows the non-linearrelationship between particle attrition and limestone content. This wasunexpected because one would expect to see attrition be significantlyhigher with 50% filler in the composite particles as compared to acomposite particle of 100% sodium bentonite. As FIG. 3 shows, attritionvalues are comparable at 0% and 50% filler. Attrition values measure thepercentage of breakage, size reduction, or fragmentation of thecomposite particles. As will be described, a modified version of ASTMmethod E-728 Standard Test Method for Resistance to Attrition ofGranular Carriers and Granular Pesticides was used to measure attrition(“Attrition Test Method”).

Attrition Test Method

This test was developed as an in-process test to monitor the granulestrength of agglomerated litter. It is based on the ASTM designation E728 Standard Test Method for “Resistance to Attrition of GranularCarriers and Granular Pesticides”. Materials Needed

-   -   100 ½-inch carbon steel balls    -   RoTap with digital timer or additional timer capable of        measuring in seconds    -   Two No. 100 mesh USA Standard Testing Sieves    -   Bottom pan for sieves    -   One 5/16-inch USA Standard Testing Sieve    -   Stiff sieve brush    -   Balance    -   Two 100 cc of product per test

Procedure First 100 cc Sample

-   -   1. Record weight of the first 100 cc sample as Initial Weight-1.    -   2. Tare a bottom pan, then place one 100-mesh sieve on top of        it. Add weighed sample to 100-mesh sieve.    -   3. RoTap sample for exactly 2 minutes with hammer down.    -   4. Weigh fines in tared bottom pan and record fines weight as        Final Weight-1. Discard fines and material on the 100-mesh        sieve.

Second 100 cc Sample

-   -   1. Record weight of the second 100 cc sample as Initial Weight-2    -   2. Distribute second 100 cc sample evenly into a clean bottom        pan. Add exactly 100 ½-inch carbon steel balls in a single layer        to sample in bottom pan.    -   3. Place a clean 100-mesh sieve on top of the bottom pan.    -   4. RoTap for exactly 1.5 minutes with hammer up (disengaged).    -   5. Tare the second bottom pan.    -   6. Using the second set of sieves, stack the 5/16-inch,        100-mesh, and the tared bottom pan.    -   7. Pour the sample and balls from the bottom pan that just came        off the RoTap into the 5/16-inch sieve stack. Make sure all        material is transferred out of the bottom pan. Manually shake        stack to separate balls from sample.    -   8. After the entire sample has passed through the 5/16-inch        sieve, remove sieve and steel balls from stack. Place the        100-mesh sieve and bottom pan with the sample onto the RoTap,        and RoTap for exactly 2 minutes with the hammer down.    -   9. Weigh the fines in the tared bottom pan and record fines        weight as Final Weight-2. Discard fines and material on the        100-mesh sieve.    -   10. Clean 100-mesh sieves as needed with stiff sieve brush.

Calculations

Calculate Attrition (wt %) by determining the weight % change of thefines from before and after it was RoTapped with the steel balls.Attrition (wt %)=[(Final Weight-2/Initial Weight-2)−(FinalWeight-1/Initial Weight-1)]×100

FIG. 4 shows that high clump strength is retained with up to about 80%filler material when the filler material is agglomerated with sodiumbentonite using a high shear agglomeration process such as a pin mixer.The clump strength of pure sodium bentonite is between 93% and 98%.

Clump Strength Test Method

Clump strength is measured by first generating a clump by pouring 10 mlof pooled cat urine (from several cats so it is not cat specific) onto a2 inch thick layer of litter. The urine causes the litter to clump. Theclump is then placed on a half inch screen after a predetermined amountof time 3 hours has passed since the particles were wetted. The screenis agitated for 5 seconds with the arm up using a Ro-Tap MechanicalSieve Shaker made by W.S. Tyler, Inc or other similar device. Thepercentage of particles retained in the clump is calculated by dividingthe weight of the clump after agitation by the weight of the clumpbefore agitation. The clump strength indicates the percentage ofparticles retained in the clump after 3 hours. Ideally, greater than90%, and more ideally, greater than 95% of the particles will beretained in a clump after 3 hours upon addition of an aqueous solution,such as deionized water or animal urine. Greater than 80% particleretention in the clump is preferred.

Composite Particle Litter Compositions

Table 1 lists a number of compositions of clumping cat litter preparedeither by (1) dry blending granular sodium bentonite and limestone or(2) agglomerating sodium bentonite and powdered limestone into compositeparticles at the ratios given.

The clump strength, attrition and bulk density were measured for allcompositions. Attrition was only measured for the pin-mixed compositeparticles, as a metric to indicate the strength of the composites. Itwas not measured on the dry blend because the individual particles wereeither pure sodium bentonite or limestone, for which attrition valuesare well established. The results shown in Table 1 below are the averagevalues from several repetitions.

TABLE 1 Lime- Na Clump Bulk Compo- stone Bentonite Method of StrengthAttrition Density sition (%) (%) Mixing (%) (%) (g/cc) A 0 100 N/A 96.03.4 68.0 B 100 0 N/A 0.0 1.7 88.0 C 30 70 Dry 90.0 N/A 73.7 Blended D 4060 Dry 88.4 N/A 75.6 Blended E 50 50 Dry 85.7 N/A 77.6 Blended F 70 30Dry 66.6 N/A 82.1 Blended I 50 50 Pin-mixed 97.1 2.1 70.4 J 70 30Pin-mixed 94.9 3.1 72.4 K 80 20 Pin-mixed 93.2 4.3 71.2 L 90 10Pin-mixed 44.8 6.4 68.9 M 95 5 Pin-mixed 0.0 8.4 68.0

Animal Litter Compositions

Although the bentonite/limestone and the bentonite/limestone/PACcomposites disclosed herein are suitable for use as an animal litter,using the bentonite/limestone and/or the bentonite/limestone/PACcomposites disclosed herein as a component to an animal litter, eitheralone or dry blended with other litter additives yield excellentresults. Combining the bentonite/limestone and/orbentonite/limestone/PAC composites disclosed herein with granular clayparticles results in an animal litter that exhibits excellent clumpstrength, odor control, tracking, color and dust control. Combining thecomposite particles with granular clay simplifies the manufacturingprocess of the animal litter. The composite particles may comprise about2 to about 100 percent by weight of the animal

Odor control of the composite particles disclosed herein when used as ananimal lifter was found to be comparable to that of a pure sodiumbentonite animal litter.

Thus, the described embodiments are to be considered in all respectsonly as illustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

1. An animal litter comprising: composite particles of a filler materialand sodium bentonite agglomerated together into the composite particles,wherein the filler material comprises from about 50% to about 80% byweight of the composite particles; wherein the animal litter has a clumpstrength of at least 80% as measured by the Clump Strength Test Method.2. The animal litter recited in claim 1, having a bulk density which isat least 10% less than the bulk density of an equivalent weight of a dryblend of sodium bentonite and filler material.
 3. The animal litterrecited in claim 1, wherein the composite particles further comprisePAC.
 4. The animal litter recited in claim 1, wherein the fillermaterial comprises limestone.
 5. The animal litter recited in claim 1,wherein the filler material comprises at least one of limestone,dolomite, calcite, calcium carbonates, sand, shale, gravel, or slate. 6.The animal litter recited in claim 1, wherein the composite particleshave a mean particle size from 0.4 mm to 2 mm.
 7. The animal litterrecited in claim 1, wherein the animal litter has a clump strength of atleast 90%.
 8. An animal litter comprising: composite particles of afiller material and sodium bentonite agglomerated together into thecomposite particles; wherein the filler material comprises from about20% to about 80% by weight of the composite particles; wherein thefiller material comprises at least one of limestone, dolomite, calcite,calcium carbonates, sand, shale, gravel, or slate; wherein the fillermaterial has a mean particle size of 0.5 mm or less; wherein the sodiumbentonite has a mean particle size of 0.25 mm or less; wherein theanimal litter has a clump strength of at least 80% as measured by theClump Strength Test Method.
 9. The animal litter recited in claim 8,wherein the filler material comprises at least one of limestone or sand.10. The animal litter recited in claim 8, wherein the bulk density ofthe animal litter is at least 10% less than the bulk density of anequivalent weight of a dry blend of sodium bentonite and the fillermaterial.
 11. The animal litter recited in claim 8, wherein thecomposite particles further comprise PAC.
 12. The animal litter recitedin claim 8, wherein the composite particles have a mean particle sizefrom 0.4 mm to 2 mm.
 13. The animal litter recited in claim 8, whereinthe animal litter has a clump strength of at least 90%.
 14. An animallitter comprising: composite particles of a filler material and sodiumbentonite, the filler material and sodium bentonite being agglomeratedtogether into the composite particles, wherein the filler material ispresent in an amount from about 30% to about 80% by weight of thecomposite particles and the sodium bentonite is present in an amountfrom about 20% to about 70% by weight of the composite particles;wherein the animal litter has a clump strength of at least 90% asmeasured by the Clump Strength Test Method.
 15. The animal litterrecited in claim 14, wherein the filler material is present in an amountfrom 40% to about 80% by weight of the composite particles.
 16. Theanimal litter recited in claim 14, wherein the filler material ispresent in an amount of about 70% by weight of the composite particles,and the sodium bentonite is present in an amount of about 30% by weightof the composite particles.
 17. The animal litter recited in claim 14,wherein the animal litter has a clump strength of at least 93%.
 18. Theanimal litter recited in claim 14, wherein the animal litter has a bulkdensity greater than 60 lb/ft³.
 19. The animal litter recited in claim14, wherein the composite particles have a mean particle size from 0.4mm to 2 mm.
 20. The animal litter recited in claim 14, wherein at leastone of: (i) the filler material has a mean particle size of 0.5 mm orless; or (ii) the sodium bentonite has a mean particle size of 0.25 mmor less.